The present invention relates to specific photochromic 3H-naphtho[2,1-b]-pyran compounds and to their use in plastics of all types, especially for ophthalmic purposes. In particular, the present invention relates to photochromic compounds, which are derived from 3H-naphtho[2,1-b]-pyrans and which, in their open form, have long wavelength absorption maxima, as a result of which violet to blue color shades can be achieved, especially when used in eyeglasses.
Various classes of dyes are known, which reversibly change their color when they are irradiated with light of particular wavelengths, especially with sunlight, because such dye molecules, when supplied with energy in the form of light, are transformed into an excited, colored state. When the energy is no longer supplied, then they leave this exited state once again and return to their normal, colorless or hardly colored state. These photochromic dyes include, for example, the naphthopyrans, which have already been described with various substituents in the prior art.
Pyrans, especially naphthopyrans and larger ring systems derived from these, are photochromic compounds, which have been the object of intensive investigations up to the present time. Although a patent was filed for the first time in 1966 (U.S. Pat. No. 3,567,605), compounds which appear to be suitable for use in eyeglasses were not developed until the 1990s.
The photochromic dyes, known in the prior art, on the one hand, frequently have inadequate absorption at long wavelengths both in the excited state and in the unexcited state. This leads to problems, even in combinations with other photochromic dyes. On the other hand, there is frequently also an excessively high temperature sensitivity with respect to the darkening and, at the same time, the brightening is too slow. Furthermore, the dyes, available in the prior art frequently have an inadequate service life. Consequently, sunglasses made with such dyes are do not have sufficient stability. The instability of such sunglasses quickly becomes noticeable due to a rapid decrease in performance and/or due to severe yellowing.
3H-naphthopyrans derived from 2-naphthols and their higher analogue compounds derived from 3H-naphthopyrans by annelation, constitute a group of photochromic dyes in which the longest wave absorption maximum of the excited form lies predominantly in the spectral range from 420 nm to 500 nm and accordingly imparts a yellow, orange or red color sensation (see U.S. Pat. Nos, 5,869,658 and 6,022,495). However, for neutral darkening photochromic glasses, powerful, violet to blue photochromic dyes are required. The violet to blue photochromic dyes presently available in the art, usually originate from the class of spiroxazines, fulgides or 2H-naphtho[1,2-b]pyrans. However, spiroxazine dyes are usually not satisfactory with respect to their high-temperature performance, while the service life of fulgide dyes and the rate of brightening of 2H-naphtho[1,2-b]pyrans are not entirely satisfactory for use in sunglasses.
The introduction of electron-shifting substituents in aryl groups in the ortho position to the pyran oxygen, for example, as described in WO 98/45281, WO 01/12619 and EP 0 945451 A1, leads to red or red violet darkening 3H-naphtho[2,1-b]pyrans. WO 01/12619 discloses compounds having one geminal aryl group which has a p-amino-substituted group and another aryl group which has an alkoxy or thioalkoxy substituent group in the meta or para position, this substitution pattern having a positive effect on the brightening rate. In the WO 98/45281, red hyperchromic compounds are described, which additionally contain an amine function predominantly in the 6 position of the 3H-naphtho[2,1-b]-pyran unit. Compounds with not pronounced basic amino groups are described in the EP 0 945 451 A1. In the excited state, these compounds have a pink to violet color, as well as an attractive service life. Appropriate substitution, especially the introduction of alkoxy groups, in the 8 position of the 3H-naphtho[2,1-b]-pyran unit brings about a bathochromic shift in the longest wavelength absorption maximum, as described in U.S. Pat. No. 5,238,981. Furthermore, compounds with dialkylamino groups in the 8 position are also disclosed. The use of nitrogen-containing heterocyclic groups as substituents in the 8 position of the 3H-naphtho[2,1-b]-pyran unit is mentioned in U.S. Pat. No. 5,990,305, as a result of which, in contrast to open-chain amino groups, an improved service life is achieved. This is also attained with substituents which contain the so-called HALS (hindered amine light stabilizer) structure elements.